Self propelled land clearing and plowing apparatus

ABSTRACT

The machine includes a frame carrying a pair of independently driven front rollers rotatable about a common axis, each carrying a set of chopper blades spaced thereabout. The frame also carries a rear roller having a pair of chopper blade sets in side-by-side relation. The blades of each set have common pitch angles with the pitch angles of the blades in the side-by-side sets extending in opposite directions. The front and rear blade sets are longitudinally aligned with the blades thereof having opposite pitch angles, thereby providing a cross chopping action as the machine advances over the ground. The rear roller is carried by a yoke mounted for pivotal movement about a vertical steering axis and a longitudinal axis to permit canting of the rear roller relative to the front roller and frame. A steering motor is provided on the yoke and drives along an arcuate track on the frame to rotate the rear roller about the vertical axis. In another form, the pair of front rollers are replaced by a single roller having arcuate blades, the latter being configured such that the blade tips transcribe the arcs of looped trochoids in the ground with the leading and trailing edges of the arcs of the trochoids intersecting such that a plowing or tilling action is provided.

United States Patent Schneider July 11,1972

[$4] SELF PROPELLED LAND CLEARING AND PLOWING APPARATUS [2|] App]. No.: 832,048

l72/57, 7], [22,554, 115, H6, H8, 119, 122, I84, 292, 6| 1; 94/50; [80/20 [56] References Cited UNITED STATES PATENTS 1,089,36l 3/ 19M i-lallbauer I 72/1 l6 751,768 2/l904 Wooster [721532 X 3,477,535 ll/l969 Wyatt ..94/50X Primary Examiner-Robert E. Palfrey Assistant Examiner-Stephen C. Pellegrino Attorney-Le Blanc and Shur [57] ABSTRACT The machine includes a frame carrying a pair of independently driven front rollers rotatable about a common axis, each can-ying a set of chopper blades spaced thereabout. The frame also carries a rear roller having a pair of chopper blade sets in side-by-side relation. The blades of each set have com mon pitch angles with the pitch angles of the blades in the side-by-side sets extending in opposite directions. The front and rear blade sets are longitudinally aligned with the blades thereof having opposite pitch angles, thereby providing a cross chopping action a the machine advances over the ground. The rear roller is carried by a yoke mounted for pivotal movement about a vertical steering axis and a longitudinal axis to permit canting of the rear roller relative to the front roller and frame. A steering motor is provided on the yoke and drives along an arcuate track on the frame to rotate the rear roller 1393mm 2/ McMonan 52 about the vertical axis. in another form, the pair of front rol- Fretts t t t t t le" are a toner arcuate blades, the 2,686,997 8/1954 Demon ..l72/540 hm" being configured such hm the blade tips transcribe the 2,775,925 l/l957 Gremer ..94/5 arcs of looped trochoids in the ground with the leading and 2,777,374 1/1957 Kinsey l72/l l6 x trailing edges of the arcs of the trochoids intersecting such 2,870,850 1/ 1959 Dethlefson.... [721554 hat a plowing or fining anion is prvid 2,930,439 3/ I960 Ahg et al ...l80/20 X 2,959,20l ll/l960 LeToumeau 1 80/20 X Chill, 14 Drawing Figures I30 O 20 4a 42 I 12 2s :26 f t 52 j 6O x Z}; fl u i 2 as 1 as 34 r, 177:5 l r 'fi P'A TE'N'TEDJUL 1 1 I972 SHEET 10F 5 INVENTOR ARTHUR F. SCHNEIDER PA'TENTEDJUL 1 I I972 3. 675 724 saw u [if s PKYENTEDJUL 1 1 m2 3.675.724

0 30 mac SELF PROPELLED LAND CLEARING AND PLOWING APPARATUS The present invention relates to a self propelled machine for land clearing and preparation. More particularly, the present invention relates to a self propelled machine of the type having front and rear roller assemblies having chopper blades spaced about the roller surfaces for the general purpose of clearing land and more specifically for clearing rough roads, right of ways, and the like, rough chopping the land and subsoiling crop land (breaking up the hard pan which develops after long use). The present machine is particularly useful for clearing heavily timbered land and has the capability of toppling, chopping and disposing in the ground trees having diameters-on the order of 12 or 13 inches. In a further form, the machine is employed for plowing and tilling the soil in crop land preparation.

One current method employed in land clearing operations utilizes a bulldozer pulling a double drummed chopper. The bulldozer is used to clear overgrowth and uproot and topple small diameter trees. The double drummed chopper drawn by the bulldozer is employed to crush and, to a limited extent, masticate the overgrowth as well as the small diameter trees uprooted by the bulldozer. This bulldozer-chopper combination can not normally be employed in areas of extremely heavy overgrowth and particularly in areas having trees of a diameter larger than 6 inches These larger trees are usually individually felled and chopped up at considerable expense. Moreover, the bulldozers are quite expensive per se and, in addition, are quite heavy, such that heavy rolling stock is required to move the bulldozer and its associated chopper to various land clearing sites. Furthermore, current practice utilizing this combination requires at least a second run over the chopped land in order to completely chop and embed the chopped material in the soil.

There is in current employment a self propelled machine for use in land clearing operations which comprises a pair of front rollers and a rear roller, each roller having a plurality of short blades arrayed thereabout. This machine also mounts a push beam for knocking over trees, the bush beam being located in front of the machine such that the front roller blades hold the roots as the machine advances and topples the tree. This machine, however, is not effective to chop completely through the overgrowth as well as the toppled trees such that the same can be implanted in the ground.

The present invention provides a self propelled land clearing machine which minimizes the above discussed shortcomings of prior land preparing and clearing devices and provides various advantages in construction, mode of operation and result over such prior devices. Generally, this is accomplished by providing a self propelled machine comprising a machine frame mounting a pair of independently driven front rollers disposed in side-by-side relation and a single rear roller. Each of the rollers carries a set of chopper blades spaced thereabout at a common pitch angle, the pitch angle of the blades on one roller extending in an opposite direction from the pitch angle of the blades on the other roller. The chopper blades preferably lie along radial extensions of the rollers at each axial position therealong such that the load carried by any blade, when the machine encounters overgrowth, trees in front of the machine or when the blades are embedded into the ground, lies substantially on a radius of the roller. The chopper blades are thus capable of carrying high loads. The chopper blades on the rear roller are arranged in a pair of blade sets in general longitudinal alignment behind the chopper blades on the front rollers, each blade set having a common pitch angle. The rear blade sets have opposite pitch angles with respect to one another and with respect to the associated longitudinally aligned blade sets of the front roller whereby a cross chopping action is provided as the machine advances over the ground. This is highly significant as a single pass of the machine over the land effectively clears and implants the chopped overgrowth including the toppled large diameter trees in the ground. This is to be contrasted with prior land clearing devices which normally require two or more passes over the same area to clear it. Moreover, the chopper blades are formed to a length as to extend through the top soil to break into and displace the hard pan below the top soil.

To clear heavier overgrowth including trees having diameters of 12 or l3 inches, the machine carries a push beam directly in front of the front roller assembly. The push beam has a slight V-configuration in plan view such that the overgrowth encountered as the machine advances is directed toward the central portion or centerline of the machine. This ensures that the overgrowth is not merely pushed out of the way laterally of the machine and it also sets up the overgrowth, principally the trees, for the cross chopping action of the blades on the front and rear rollers. Moreover, the machine is of such weight and the blades are particularly configured such that a combined tree toppling and chopping action is efficiently provided. For example, when the machine encounters a tree having a diameter of about l2 inches and a laterally extending root system within a range of about 2 feet from the land surface, the elongated chopper blades initially sever and chop through the root system of the tree adjacent the surface of the ground well in advance of the engagement of the push beam against the tree. As the machine advances toward the tree, the roots are continuously chopped and severed. Upon engagement of the push beam against the tree, further advancement of the machine readily and easily topples the tree as its root system on the machine side of the tree has been completely severed. Moreover, the V-shaped push beam tends to locate the toppled tree directly in the path of the machine. As the machine advances over the toppled tree, the pitched front roller blades either chop through the tree trunk or tend to align the tree trunk and parts thereof between the blades. In the first instance, the tree trunk and parts thereof are effectively chopped through and implanted. In the second instance, the tree trunk and its parts are set up for through chopping action by the rear roller. Thus, by the unique disposition of the blades about the front and rear roller assemblies and their novel configuration, an effective chopping and cross chopping action as well as implantation of the chopped material is provided.

The machine can be employed in extremely rough terrain and still provide efficient land clearing operations with only a single pass of the machine due to a novel, unique mounting between the frame and the rear roller assembly. The rear roller assembly is carried by the frame at primary and secondary pivotal mountings. The primary pivotal mounting is provided for pulling the rear roller assembly and comprises a guide block carried by the rear roller support frame for movement along an arcuate track carried by the main machine frame. This rear roller frame is secondarily mounted to the main frame for pivotal movement about a vertical axis at a point spaced above the primary pivotal mounting. A drive motor is carried by the rear roller guide block and drives the rear roller frame about the vertical axis along the arcuate track of the main frame as to steer the machine. To facilitate operations in rough terrain, the rear roller assembly is also mounted for canting movement about a longitudinal axis which, for all angular positions of the rear roller frame about the vertical axis, extends through the primary pivotal mounting. In this manner, the rear roller can be canted or inclined relative to the front roller.

Another important feature of the present invention is the provision of an independent drive system for the front rollers. A suitable engine is carried by the frame and drives a main shaft connected through a differential and separate shafts to separate chain drives for the rollers. Selectively actuated brakes are provided each of the rollers and it will be seen that the rollers can be driven independently to assist in steering the machine.

It is a further important feature of the present invention that the present machine can be employed for plowing and tilling operations. To accomplish this, the front roller chopper blades are replaced by a roller having blades specifically designed and configured for plowing or tilling operations while the rear roller is replaced by a lightweight roller system, for example, a plurality of tires or a disc or other soil conditioning equipment. The plowing blades on the substitute front roller are arcuate in cross section and are disposed thereabout at a pitch angle of about 60". These blades are spaced one from the other about the periphery of the roller and are configured such that next adjacent blade tips transcribe the arcs of looped trochoids in the ground, the trochoids being longitudinally spaced one from the other with their respective leading and trailing arcs intersecting at a point below the periphery of the support roller a distance greater than one-fourth of the length of the blade measured on the roller radius. By fonning the blades to these requirements, the soil is lifted, turned over and deposited at a point transversely offset from its initial undisturbed position. By utilizing plow blades on a roller, the life of the blades is greatly extended as the blades are not constantly immersed in the soil as are the blades of a conventional plow or tiller.

As will be appreciated, the plowing blades, in effect act as an augur tending to displace the machine laterally. To preclude this, a ring colter is provided along the side of the drum away from the tilling action, i.e., toward the direction of lateral movement of the machine. The colter is specifically configured, i.e., the outer face is arcuately beveled, to displace the machine in the opposite lateral direction thereby compensating for the tendency of the machine to move laterally due to plowing action. The colter also cuts the sward and forms a smooth furrow to facilitate alignment of the machine for the next adjacent pass.

Accordingly, it is a primary object of the present invention to provide a novel, improved self propelled machine for chopping through and implanting cleared overgrowth including large diameter trees.

It is another object of the present invention to provide a self propelled machine for clearing heavily timbered land having trees on the order of 12 or l3 inches in diameter.

It is still another object of the present invention to provide a self propelled land clearing machine of the type having front and rear rollers mounting blades specifically configured to provide a cross chopping action.

It is still another object of the present invention to provide a self propelled land clearing machine having a push beam configured to direct overgrowth including trees toward the central portion of the path over which the machine advances.

It is a further object of the present invention to provide a self propelled machine for land clearing operations of the type having a front and rear rollers with the rear roller drum mounted for steering about a vertical axis and for canting movement about a longitudinal axis for all angular positions of the rear roller about the vertical axis.

It is a still further object of the present invention to provide a self propelled land clearing machine having a pair of independently driven front roller drums for steering purposes.

It is a related object of the present invention to provide a self propelled machine of the type having a front roller and mounting blades thereon specifically configured for plowing operations.

It is a further related object hereof to provide a novel sectional plow blade.

These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings, wherein:

FIG. I is a side elevational view of a land clearing and preparing machine constructed in accordance with the present invention;

FIG. 2 is a cross sectional view thereof taken generally about on line 2-2 in FIG. 1;

FIG. 3 is a cross sectional view thereof taken generally about on line 3-3 in FIG. I;

FIG. 4 is a rear elevational view of the machine of FIG. I;

FIG. 5 is an enlarged fragmentary cross sectional view of the primary pivotal mounting between the main frame and rear roller frame assembly;

FIG. 6 is an enlarged fragmentary view of the edge on one of the chopper blades of the rollers;

FIG. 7 is a plan view of the pattern transcribed in the ground by the blades on the front and rear rollers and further illustrates the cross chopping action;

FIGS. 80, 8b and 8c are schematic fragmentary, side elevational views of the machine illustrating the manner in which a tree is toppled and chopped through;

FIG. 9 is a fragmentary plan view of a roller having plowing blades disposed thereabout and a colter for use with the machine hereof;

FIG. 10 is an enlarged cross sectional view thereof taken about on line III-I0 in FIG. 9;

FIG. I] is an enlarged cross sectional view of one of the plow blades illustrated in FIG. [0; and

FIG. 12 is a side elevational view illustrating the plowing action of the blades on the roller illustrated in FIG. 9 as the machine advances over the land.

Referring now to the drawings, specifically to FIG. I, there is illustrated a self propelled land clearing and preparing machine constructed in accordance with the present invention and comprising a main frame, generally indicated at 10, carrying front and rear roller frame assemblies generally indicated at 12 and 14 respectively. Main frame I0 includes a central structural tubular member [6 suitably joined at its forward end to a transversely extending structural tubular member I8. This substantially T-shaped frame supports a platform 20 on which is mounted a suitable power plant 22, a cab 24 for the machine operation, and suitable controls, not shown, for the machine.

Depending side tubular structural members 26 are suitably secured at their upper ends to the ends of cross member I8 and at their lower ends to journal boxes indicated at 28 for mounting therebetween a front roller assembly generally indicated at 30. The front roller frame assembly I2 includes a central arcuately extending structural tubular member 32 connected at one end to cross member 18 and which extends forwardly about and in spaced relation from roller assembly 30 to a point in front of the roller assembly 30. A pair of forwardly extending side structural tubular members 34 are suitably connected at their rear ends to journal boxes 28 and at their front ends to a transversely extending tubular push beam 36. As noted in FIG. 2, push beam 36 is slightly V-shaped in plan view with the central apex portion thereof being suitably secured to the lower end of arcuate central member 32.

The rear frame assembly 14 is coupled to the main frame 10 by a primary pivotal mounting, generally indicated 40, and a secondary pivotal mounting generally indicated 42, rear frame 14 carrying a roller 44. Rear frame [4 includes a shaft 46 pivotally mounted within an outer sleeve 48 to which is suitably secured a reduced diameter hon'zontaliy extending tubular member 50. Member 50 is received within the main tubular member I6 and has a pair of elongated slots 51 through which are received bolts 53 for securing member 50 to main frame 10. Rear frame assembly 14 is thus free for limited longitudinal movement relative to main frame 10 whereby the thrust between the rear frame assembly and main frame I0 is carried by the primary pivotal mounting I4. The lower end of shaft 46 carries a mounting block 52 having a transversely extending arcuate track 54 which may be provided with suitable bearings along its interior walls as desired. Rear frame I4 further includes a structural cross tubular member 56 having, as best seen in FIG. 4, a central arcuate portion 58 received within the arcuate element or track 54 on mounting block 52. The track 54 and portion 58 lie on arcs of a circle having its center at 60. It will thus be apparent that the rear frame assembly 14 is pivotally mounted about a longitudinal axis indicated at 60 in FIGS. I and 4.

A pair of side, vertically extending, structural tubular members 62 are suitably secured at their upper ends to the outer ends of cross member 56 with their lower ends being suitably secured to journal boxes 64. A yoke like frame assembly extends between journal boxes 64 and primary pivotal mounting 40 and comprises a pair of forwardly and upwardly inclined structural tubular members 66 and a pair of horizontally inwardly extending structural tubular members 68 suitably secured at their forward ends on opposite sides of a mounting block 70. As seen in FIG. 5, block 70 is centrally bored as at 71 and stepped to provide a pair of outer bearing races. A shaft 72 is received within bore 71 and mounts a pair of axially spaced collars 74 and 76 on which are carried the inner bearing races. A plurality of ball bearings 78 are disposed between the races and shaft 72 has a threaded extension 80 for receiving a nut 82 for retaining the collars 74 and 76 on shaft 72 with block 70 being rotatably about the axis of shaft 72. The axis of 1 shaft 72 and hence the pivotal axis of mounting block 70 is coincident with the axis 60 and it will thus be appreciated that the rear frame assembly 14 is mounted for pivotal movement about the vertical axis of shaft 46, and for canting movement about the horizontal axis 60.

Referring now to FIGS. 1 and 2, the frame also includes a central vertically extending structural tubular member 84, opposite ends of which are suitably secured to main frame member 16 and the forward portion of a structural platform 86. A pair of side structural tubular members 88 are suitably connected at their forward ends to journal boxes 28 and at their rear ends to the underside of platform 86. The rear edge of platform 86 is arcuately cutout as at 90 with the center of the are lying coincident with the axis of shaft 46. An arcuate structural tubular member 92, also coincident with the arc of a circle having its center on the axis of shaft 46, is suitably connected at opposite ends to inwardly directed portions 94 of platform 86 and is spaced from edge 90 as to leave an arcuate space therebetween.

An arcuate track 96 is provided along the upper surface on platform 86 directly adjacent edge 90 and carries gear teeth 98. A guide block 100 has a transversely extending arcuate bore formed therein which slidably receives the arcuate tubular member 92. Suitably bearings may be provided ifdesired in the bore of guide block 100. The forward end of shaft 72 is suitably secured as by bolts 102 within a recess opening through the rear portion of guide block 100. It will thus be appreciated that guide block 100 traverses along tubular member 92 as rear roller assembly 38 rotates about the vertical axis of shaft 46. A motor, preferably a variable displacement hydraulic motor 104, is suitably secured to guide block 100 and drives a shaft carrying a gear 106 for meshing engagement with the gear teeth 98 on track 96. When the steering motor is not employed, it should lie in a null position that will allow the steering mechanism to be free for traversing movement along track 96 in either direction as necessary due to forces developed by unbalanced loads on the rear roller assembly. The steering control has five positions; a mid position or null, a position either side of null to lock the steering motor such that gear 106 lies in locked meshing engagement with gear teeth 98 to preclude movement of the rear frame assembly about the axis of shaft 46 and a position on either side of the lock positions for driving the steering motor in the selected direction.

Referring now particularly to FIG. 3, front roller assembly 30 comprises a pair of roller drums 108 and 110 suitably secured on shafts 112 and 114 respectively. Shaft 112 extends the full width of the machine and its opposite ends are carried in suitable bearings in journal boxes 28. Shaft 114 has a reduced axial extent and an enlarged diameter. Shah 114 lies concentrically about shaft 112 on bearings 116 disposed between shafts I12 and 114 whereby these shafts are independently rotatable. Each of drums 108 and 110 is hollow and has a plurality of axially spaced reinforcing rings 118 about the inner periphery thereof. Suitable openings, not shown, in the outer sides of the drums, are provided whereby water, sand or other heavy material may be disposed within the drums for purposes as will become clear from the ensuing description.

As seen in FIGS. 1 and 3, sprockets I20 and 122 are suitably secured on the outer side of drums 108 and respectively and a pair of heavy duty belt chains [24 and 126 engage about the respective sprockets and respective drive gears 128 and 130. The drive gears I28 and 130 are carried on shafts 132 and 134 respectively, the latter shafts being driven through a transmission, clutch and differential arrangement generally indicated at 136. The differential serves to transmit power to either or both of the roller drums I08 and "0 through their respective gear, drive chain and sprocket arrangements. Brakes I36 and 138 for the shafts I32 and I34 respectively are provided whereby the drums can be selectively and independently driven, to assist the steering motor I04 to steer the machine.

it is a unique feature of the present invention that the blades on the front and rear rollers are arranged to provide a cross chopping action. Particularly, chopper blades 140 and M2 are spaced about drums I08 and 110 respectively with the blades on each drum having a common pitch angle. The pitch angle of the blade set on one drum, however, is opposite to the pitch angle of the blade set on the other drum. Moreover, the blades on each drum are configured such that each blade constitutes an extension of the radius of the drum at any axial point along the drum. Specifically, the root line of the blade lies in a plane passing through the blade and drum with opposite end portions of the blade lying outside the plane on opposite sides thereof. To provide the cross chopping action, the blades on the rear roller 44 are arranged in a pair of blade sets with each blade set being allochiral with respect to the other blade set. The blade sets on the rear drum are in longitudinal alignment with the blades on the respective front drums 108 and I10 and the pitch angle of the longitudinally aligned blade sets extends oppositely such that a track as seen in FIG. 7 is formed in the ground. As the machine advances, the tracks formed in the ground by the front and rear rollers intersect one another, thereby providing a cross chopping action.

in a preferred embodiment hereof, 5 foot diameter drums are employed with the blades on the front drums being 2 feet in length providing an overall front roller diameter of 9 feet. The blade length on the rear drum 44 is about 18 inches providing an overall rear roller diameter of about 8 feet. The blades per so are preferably formed on steel having a width at their root of about 6 inches and tapering linearly to a pointed edge. With a 5 foot diameter drum, the blades should be spaced at their root about 14 inches apart. The machine has an overall length about 26 feet, a width about 12 feet and a height of about l4 feet. The weight of a machine constructed to these dimensions without material in the drums is about 25 tons and with water in the drums is about 37 tons. With an even weight distribution on the drums and the described tooth configuration, a 35 ton per square inch of force can be applied to a tree trunk or other overgrowth as the machine advances. The pitch angle of the blade is preferably 30.

in use, the machine will exert about 2 pounds per square inch pressure on the ground with the machine lying at a level with respect to the ground surface such that the peripheries of the drums are spaced about 4 inches from the ground surface. This provides excellent ground flotation characteristics while simultaneously providing a force adequate to crush or chop through overgrowth in the path of the machine including trees having a diameter on the order of 12 or 13 inches. Referring to FIGS. 80, 8b and 8c, the machine is advanced along the ground by the driving action of the front rollers. The blades normally extend into the ground to a depth of about l8 to 20 inches thus cross chopping the ground including the hard pan and any overgrowth lying in the path of the machine. As it approaches a tree, the blades chop through and completely sever the root system lying on the one side of the tree to a depth less than 20 inches prior to engagement of the push beam 36 against the tree trunk. When the push beam 36 engages the tree, it will be appreciated that the root system has been cut through from a point about 5 feet from the tree and beyond. Thus, the tree is weakened and easily toppled by further advancement of the machine. As the tree is being toppled as illustrated in FIG. 8b, the blades continue to chop through and sever the root system until finally the tree is completely toppled. At this point, the blades ride over and chop completely through the tree trunk per se as the machine advances thereover. Note that the V-shaped push beam 36 tends to locate and directs the tree and other overgrowth toward the center of the path of the machine rather than pushing the tree and other overgrowth outwardly out of the path of advancement of the machine. Moreover, as the blades contact the tree and other overgrowth, they also tend to direct the tree and overgrowth toward the center of the machine track. As the machine passes over the tree, the tree is first chopped through in one direction by the blades of the front rollers and then chopped through in one direction by the blades of the front rollers and then chopped through in an opposite direction by the blades of the rear roller. This assures that the tree trunk will be completely chopped through. Moreover, the blades and the rollers implant the chopped material directly into the ground. Note that those portions of the trunk which engage between the blades on the front roller, will be chopped through by the rear roller as its blades will chop at an angle relative to the angle chopped by the front blades whereby the trunk or overgrowth parts disposed between the front roller blades will be chopped through and implanted by the rear roller. To assist in the chopping operation, the blade edges may be formed to a saw tooth serrated pattern as indicated at 150 in FIG. 6. a

It is a further feature of the present invention that the front and rear roller drum assemblies can be readily and easily replaced by different types of rollers for performing other operations such as packing, plowing and the like. To this end, the journal boxes 28 and 64 on the front and rear roller assemblies are provided with a lower cross bar 154 suitably secured to the journal boxes 28 as by bolts 156. By removing this lower cross bar I54 and the bolt chains, the machine can be lifted from the rollers 30 and 38 with other roller shafts then being received within the journal boxes 28. For example, rollers with packing feet can be substituted for the illustrated bladed rollers. It is a particular and significant feature of the present invention that a roller drum assembly specifically configured to provide a land plowing or tilling operation can be substituted for the front roller assembly shown in FIG. 1. Referring now to FIGS. 9 and 10, there is shown a roller drum 160 having a plurality of arcuate blades 162 spaced thereabout. The blades have a constant pitch angle relative to the drum, preferably 60. The blades per se are arcuately shaped with the root of the blades lying on a radius of the drum at any axial position along the drum. The angle formed by the drum radius extended through the root and a line drawn from the root of the tooth through its tip is preferably about 30 as indicated at e in FIG. 10. The blades 162 have a width of about 2 feet along a radius of the drum with a root width of 6 inches. The drum 160 is preferably feet in diameter and 10 feet in length.

The blades I62 are preferably sectional with the root portions 164 (See FIG. ll) of the blades 162 being suitably permanently secured to the drum. Tip portions 166 are provided each of the blades 162 in longitudinal sections, preferably in three sections, whereby one or more of the sections can be readily and easily replaced upon damage to the blade tips. Particularly the tip portions of the blade roots 164 are stepped as at I68 with the root portions of the tip sections being correspondingly stepped as at I70. Bolt holes are provided through the stepped portions 168 and I70 to receive bolts 172 to rigidly secure the blade tip and root portions one to the other. If desired, the back face of the blade tip portions can be enlarged or widened as at 174 to protect the nuts and bolts from erosion by the soil. The blades have a width, and are spaced one from the other about the periphery of the drum and are arcuate in cross section such that the next adjacent blade tips, as seen in FIG. 12, transcribe the arcs of looped trochoids below the ground, the trochoids being longitudinally spaced one from the other with the leading and trailing arcs indicated at b and c respectively intersecting at a point below the periphery of the drum a distance greater than one-fourth of the width of the blade. Preferably, this intersection should lie at a point three-fourths of the blade width from the drum periphery. By employing blades formed to the foregoing configuration, the soil will be lifted and turned and redeposited on the ground at a point laterally spaced from its initial position. More specifically, as seen in FIG. 12, the blade is arcuate in cross section such that the blade tip enters the ground at a point very nearly normal to the ground as indicated at 3. As the roller advances, the blade root follows the blade tip into the soil with minimum disturbance of the soil until the root of the blade is substantially normal to the surface of the soil. Further advancement of the roller, causes withdrawal of the blade from the soil with the latter concommitantly being lifted, turned and displaced laterally. Particularly, the lifted soil lies in the area of the looped trochoid below the ground surface and the soil tends to run laterally along the blade face thereby being turned and redeposited at a substantially laterally adjacent position.

By employing plow blades constructed in accordance with the foregoing on a roller drum, the hard pan, i.e., that compacted ground just below conventional plow depth of about I2 inches, is also turned and broken up thereby providing a greater depth of top soil with which to retain moisture. With the foregoing described plow blades having a width of 2 feet, it is thus possible to break up hard pan as deep as 20 inches thereby providing improved growing conditions and permitting the root systems to extend into the deeper moisture zones.

It will be appreciated that other roller drum diameters, blade widths and spacing can be provided to accomplish the foregoing described plowing action of the present invention. For example, the following table indicates the preferable linear dimensions between the lands, blade tips and blade roots indicated at k, I and m respectively in FIG. I2.

Drum Diameter The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

l. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, and drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, said front roller means including a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blade sets on said front roller means being in substantial longitudinal alignment with the respective sets of blades on the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances thereover.

2. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, and drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, said front roller means including a pair of laterally spaced rollers, means mounting said rollers for independent rotation relative to one another, said drive means including means for rotating said rollers independently of one another, a plurality of blades being spaced about each of said front rollers, the blades on each of said front rollers extending at substantially common pitch angles with the blades carried by one of said front rollers having pitch angles opposite to the pitch angles of the'blades carried by the other of said front rollers, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blades carried by the front rollers being in substantial longitudinal alignment with the respective sets of blades carried by the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances thereover.

3. A machine for clearing land comprising; an elongated frame, front roller means cam'ed by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, said mounting means including a yoke assembly, an arcuate guide carried by one of said frame and yoke assembly, means carried by the other of said frame and said yoke assembly and coupled to said guide, said steering means being cooperable between said frame and said yoke assembly to pivot said yoke assembly about said vertical axis.

4. A machine according to claim 3 wherein said normal axis is spaced above said oller axis, said rear roller being mounted for pivotal movement about said normal axis to permit inclination of said rear roller relative to the horizontal.

5. A machine according to claim 3 wherein said front roller means includes a pair of laterally spaced rollers, and means mounting said rollers for independent rotation relative to one another, said drive means including means for rotating said rollers independently of one another.

6. A machine according to claim 3 wherein said mounting means includes connecting means between said frame and said yoke assembly for pivoting said yoke assembly about the vertical axis and including an arcuate track lying in said plane, said yoke assembly having an arcuate element engageable along said track to support said frame irrespective of a predetermined angular disposition of said rear roller about said normal axis.

7. A machine according to claim 3 wherein said front roller means includes a plurality of blades spaced thereabout and arranged in a pair of side-by-side blade sets, the blades of each set extending at substantially common pitch angles with the blades of one side having pitch angles opposite to the pitch angles of the blades of the other set, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blade sets on said first roller means being in substantial longitudinal alignment with the respective blade sets on the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine is advanced thereoven 8. A machine according to claim 7 including a push beam carried by said frame and disposed forwardly of said front roller means, said push beam extending between the opposite sides of the machine.

9. A machine according to claim 8 wherein said front roller means includes a pair of laterally spaced front rollers, and means mounting said rollers for independent rotation relative to one another, said drive means including means for rotating said rollers independently of one another, a blade set being mounted on each of said front rollers.

10. A machine according to claim 5 wherein said rollers are hollow, means for permitting ingress of material into said rollers for weighting the latter, said drive means including an engine, a drive shaft and a differential for driving said rollers independently from said drive shaft.

ll. A machine according to claim 3 including means releasably securing said front roller means and said rear roller to said frame.

12. A machine according to claim 3 wherein said rear roller is rotatable about said vertical axis into a position wherein said plane and the long axis of said frame lie in non-perpendicular relation one to the other, said rear roller being pivotable about said normal axis when said rear roller obtains said position.

13. A machine according to claim 3 wherein said front roller means comprises a substantially cylindrically shaped elongated roller pivotally carried by said frame and having a plurality of blades extending from the periphery thereof for immersion in the ground, said blades extending in an axial direction relative to said roller and forming at least portions of helices about said member, said blades being spaced one from the other about said roller and having a width and common arcuate cross sections such that next adjacent blade tips transcribe the arcs of longitudinally spaced looped trochoids below the surface of the ground as the machine advances thercalon g, the leading and trailing arcs of the next adjacent trochoids intersecting at a point below the periphery of said roller a distance greater than one-quarter of the width of the blade whereby the soil within the confines of said looped trochoids is lifted, turned and redeposited on the ground at a point laterally spaced from its initial undisturbed position.

14. An apparatus according to claim 13 wherein said blades have roots which extend radially from said roller, the blades being tapered in cross section to form sharp blade edges.

15. An apparatus according to claim 13 wherein said blade tips enter the ground along a line extending generally perpendicular to the surface of the ground to facilitate blade penetration into the ground.

16. An apparatus according to claim 13 including a colter on one side of said roller, said colter being configured to displace the roller in a lateral direction opposite to the lateral direction in which the helical blades tend to displace the roller as the roller advances along the ground.

l7. An apparatus according to claim 13 wherein said colter includes a ring about said roller and having a diameter larger than the diameter of said roller and blade combination.

18. A machine for clearing land comprising: an elongated frame; a pair of rollers, means mounting said rollers in spaced side-by-side relation one to the other to a front portion of said frame for independent rotation relative to one another; means carried by said machine for rotating said front rollers independently of one another to advance said machine along the ground, a plurality of blades spaced about each of said front rollers, the blades on each of said front rollers extending at substantially common pitch angles with the blades carried by one of said front rollers having pitch angles opposite to the pitch angles of the blades carried by the other of said front rollers, a rear roller carried by said frame adjacent a rear portion thereof; said rear roller carrying a plurality of blades thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blades carried by the front rollers being in substantial longitudinal alignment with the respective sets of blades carried by the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances, and means cooperable with one of said rear roller and pair of front rollers for steering said machine.

l9. A machine according to claim 18 including a push beam carried by said frame and disposed forwardly of said front roller means, said push beam extending between the opposite sides of the machine and having a generally concave shape, the lateral ends of said push beam being spaced forwardly from said front roller means a distance greater than the distance between the central portion of said push beam and said front roller means.

20. A machine according to claim 18 including means mounting said rear roller to said frame for pivotal movement about a generally vertical axis and for pivotal movement about an axis generally normal to a plane containing said vertical axis and the rear roller axis; said mounting means including a yoke assembly and an arcuate guide carried by said frame, means carried by said yoke assembly and coupled to said guide, and steering means cooperable between said frame and said yoke assembly to pivot said yoke assembly about said vertical axis.

21. A machine according to claim 20 including connecting means between said frame and said yoke assembly for pivoting said yoke assembly about the normal axis and including an arcuate track lying in said plane, said yoke assembly having an arcuate element engageable along said track to support said frame irrespective of angular disposition of said rear roller about said normal axis within a predetermined range.

22. A machine for clearing land comprising: an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof and for pivotal movement about a generally vertical axis, said front roller means including a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blade sets on said front roller means being in substantial longitudinal alignment with the respective sets of blades on the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a crow chopping pattern in the land as the machine advances thereover, means for driving one of said front roller means and said rear roller to advance the machine along the ground, and a push beam carried by said frame and disposed forwardly of said front roller means, said push beam extending between opposite sides of the machine.

23. A machine according to claim 22 wherein said push beam has a generally concave shape, the lateral ends of said push beam being spaced forwardly of said front roller means a distance greater than the distance between the central portion of said push beam and said front rollers.

24. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, and a push beam being carried by said frame and disposed in front of said front roller means, said push beam extending between the opposite sides of the machine and having a generally concave shape, the lateral ends of said push beam being spaced forwardly of said front roller means a distance greater than the distance between the central portion of said push beam and said front roller means. 

1. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, and drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, said front roller means including a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blade sets on said front roller means being in substantial longitudinal alignment with the respective sets of blades on the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances thereover.
 2. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, and drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, said front roller means including a pair of laterally spaced rollers, means mounting said rollers for independent rotation relative to one another, said drive means including means for rotating said rollers independently of one another, a plurality of blades being spaced about each of said front rollers, the blades on each of said front rollers extending at substantially common pitch angles with the blades carried by one of said front rollers having pitch angles opposite to the pitch angles of the blades carried by the other of said front rollers, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blades carried by the front rollers being in substantial longitudinal alignment with the respective sets of blades carried by the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances thereover.
 3. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, drive means carried by said frame and drivingly Coupled to said front roller means to rotate the latter and thereby advance the machine, said mounting means including a yoke assembly, an arcuate guide carried by one of said frame and yoke assembly, means carried by the other of said frame and said yoke assembly and coupled to said guide, said steering means being cooperable between said frame and said yoke assembly to pivot said yoke assembly about said vertical axis.
 4. A machine according to claim 3 wherein said normal axis is spaced above said roller axis, said rear roller being mounted for pivotal movement about said normal axis to permit inclination of said rear roller relative to the horizontal.
 5. A machine according to claim 3 wherein said front roller means includes a pair of laterally spaced rollers, and means mounting said rollers for independent rotation relative to one another, said drive means including means for rotating said rollers independently of one another.
 6. A machine according to claim 3 wherein said mounting means includes connecting means between said frame and said yoke assembly for pivoting said yoke assembly about the vertical axis and including an arcuate track lying in said plane, said yoke assembly having an arcuate element engageable along said track to support said frame irrespective of a predetermined angular disposition of said rear roller about said normal axis.
 7. A machine according to claim 3 wherein said front roller means includes a plurality of blades spaced thereabout and arranged in a pair of side-by-side blade sets, the blades of each set extending at substantially common pitch angles with the blades of one side having pitch angles opposite to the pitch angles of the blades of the other set, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blade sets on said first roller means being in substantial longitudinal alignment with the respective blade sets on the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine is advanced thereover.
 8. A machine according to claim 7 including a push beam carried by said frame and disposed forwardly of said front roller means, said push beam extending between the opposite sides of the machine.
 9. A machine according to claim 8 wherein said front roller means includes a pair of laterally spaced front rollers, and means mounting said rollers for independent rotation relative to one another, said drive means including means for rotating said rollers independently of one another, a blade set being mounted on each of said front rollers.
 10. A machine according to claim 5 wherein said rollers are hollow, means for permitting ingress of material into said rollers for weighting the latter, said drive means including an engine, a drive shaft and a differential for driving said rollers independently from said drive shaft.
 11. A machine according to claim 3 including means releasably securing said front roller means and said rear roller to said frame.
 12. A machine according to claim 3 wherein said rear roller is rotatable about said vertical axis into a position wherein said plane and the long axis of said frame lie in non-perpendicular relation one to the other, said rear roller being pivotable about said normal axis when said rear roller obtains said position.
 13. A machine according to claim 3 wherein said front roller means comprises a substantially cylindrically shaped elongated roller pivotally carried by said frame and having a plurality of blades extending from the periphery thereof for immersion in the ground, said blades extending in an axial direction relative to said roller and forming at least portions of helices about said member, said bladEs being spaced one from the other about said roller and having a width and common arcuate cross sections such that next adjacent blade tips transcribe the arcs of longitudinally spaced looped trochoids below the surface of the ground as the machine advances therealong, the leading and trailing arcs of the next adjacent trochoids intersecting at a point below the periphery of said roller a distance greater than one-quarter of the width of the blade whereby the soil within the confines of said looped trochoids is lifted, turned and redeposited on the ground at a point laterally spaced from its initial undisturbed position.
 14. An apparatus according to claim 13 wherein said blades have roots which extend radially from said roller, the blades being tapered in cross section to form sharp blade edges.
 15. An apparatus according to claim 13 wherein said blade tips enter the ground along a line extending generally perpendicular to the surface of the ground to facilitate blade penetration into the ground.
 16. An apparatus according to claim 13 including a colter on one side of said roller, said colter being configured to displace the roller in a lateral direction opposite to the lateral direction in which the helical blades tend to displace the roller as the roller advances along the ground.
 17. An apparatus according to claim 13 wherein said colter includes a ring about said roller and having a diameter larger than the diameter of said roller and blade combination.
 18. A machine for clearing land comprising: an elongated frame; a pair of rollers, means mounting said rollers in spaced side-by-side relation one to the other to a front portion of said frame for independent rotation relative to one another; means carried by said machine for rotating said front rollers independently of one another to advance said machine along the ground, a plurality of blades spaced about each of said front rollers, the blades on each of said front rollers extending at substantially common pitch angles with the blades carried by one of said front rollers having pitch angles opposite to the pitch angles of the blades carried by the other of said front rollers, a rear roller carried by said frame adjacent a rear portion thereof; said rear roller carrying a plurality of blades thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blades carried by the front rollers being in substantial longitudinal alignment with the respective sets of blades carried by the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances, and means cooperable with one of said rear roller and pair of front rollers for steering said machine.
 19. A machine according to claim 18 including a push beam carried by said frame and disposed forwardly of said front roller means, said push beam extending between the opposite sides of the machine and having a generally concave shape, the lateral ends of said push beam being spaced forwardly from said front roller means a distance greater than the distance between the central portion of said push beam and said front roller means.
 20. A machine according to claim 18 including means mounting said rear roller to said frame for pivotal movement about a generally vertical axis and for pivotal movement about an axis generally normal to a plane containing said vertical axis and the rear roller axis; said mounting means including a yoke assembly and an arcuate guide carried by said frame, means carried by said yoke assembly and coupled to said guide, and steering means cooperable between said frame and said yoke assembly to pivot said yoke assembly about said vertical axis.
 21. A machine according to claim 20 including connecting means between said frame and said yoke assembly for pivotIng said yoke assembly about the normal axis and including an arcuate track lying in said plane, said yoke assembly having an arcuate element engageable along said track to support said frame irrespective of angular disposition of said rear roller about said normal axis within a predetermined range.
 22. A machine for clearing land comprising: an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof and for pivotal movement about a generally vertical axis, said front roller means including a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, said rear roller carrying a plurality of blades spaced thereabout and arranged in a pair of spaced side-by-side blade sets, the blades of each rear blade set extending at substantially common pitch angles with the blades of one set having pitch angles opposite to the pitch angles of the blades of the other set, the blade sets on said front roller means being in substantial longitudinal alignment with the respective sets of blades on the rear roller, the blades of the substantially aligned sets having opposite pitch angles to provide a cross chopping pattern in the land as the machine advances thereover, means for driving one of said front roller means and said rear roller to advance the machine along the ground, and a push beam carried by said frame and disposed forwardly of said front roller means, said push beam extending between opposite sides of the machine.
 23. A machine according to claim 22 wherein said push beam has a generally concave shape, the lateral ends of said push beam being spaced forwardly of said front roller means a distance greater than the distance between the central portion of said push beam and said front rollers.
 24. A machine for clearing land comprising; an elongated frame, front roller means carried by said frame for rotation about a generally horizontal axis; a rear roller, means carried by said frame for mounting said rear roller for rolling movement about the axis thereof, for pivotal movement about a generally vertical axis, and for pivotal movement about an axis generally normal to a plane containing said vertical axis and said roller axis; means for pivoting said rear roller about said vertical axis to steer said machine, drive means carried by said frame and drivingly coupled to said front roller means to rotate the latter and thereby advance the machine, and a push beam being carried by said frame and disposed in front of said front roller means, said push beam extending between the opposite sides of the machine and having a generally concave shape, the lateral ends of said push beam being spaced forwardly of said front roller means a distance greater than the distance between the central portion of said push beam and said front roller means. 